Tea is a beverage traditionally made by infusing the dry leaves of the plant Camellia sinensis in boiling water. Tea is (with the exception of water) probably the world's most popular beverage and, in some parts of the world, has traditionally been considered to have health-promoting potential. Recently, extensive laboratory research and epidemiologic studies have shown that many compounds present in tea show bioactivity and may be useful, for example, in treating a variety of illnesses and/or in producing enhanced physical or mental performance.
Polyphenolic compounds such as catechins and theaflavins have been shown to be particularly valuable. Some of the benefits of tea polyphenols may be directly linked to their antioxidant properties. The purported benefits include lowering blood lipid levels (e.g. cholesterol), anti-inflammation effects and anti-tumour effects.
Another tea compound which has been shown to have bioactivity is the amino acid theanine. For example, it is reported that theanine stimulates a-waves in the mammalian brain and bestows a relaxed but alert mental state to the individual.
Besides bioactive compounds, tea also contains compounds which are valued for their sensory qualities. In particular, tea has a unique aroma and is rich in aroma compounds.
Although some of the benefits of tea compounds may be apparent at consumption rates as low as a few cups per day, many individuals do not even achieve this modest consumption rate on a long term basis. Furthermore, tea beverages are less convenient to prepare than beverages prepared from non-tea-based beverage precursors, such as instant coffee, owing to the relatively slow rate of infusion of tea leaves and slow rate of dissolution of tea powders. Also, there is an increasing desire amongst consumers for products which deliver new sensory experiences but which products are derived from natural sources.
There have therefore been many previous efforts to provide products with enhanced levels of compounds derived from tea. In many cases the previous efforts have employed a process wherein the tea compounds are extracted from tea leaves using a solvent, such as water. For example, WO 2006/037511 (Unilever) discloses a process for preferentially extracting theanine from tea plant material which involves a short cold water extraction. One drawback with the known processes is that time and energy are employed to remove the large amounts of solvent required for exhaustive extraction.
Tea stem is a rich source of tea actives. WO 2006/021317 (Unilever) discloses a process comprising the steps of: (i) harvesting a source of tea plant material comprising stem and leaf material; (ii) physically separating the stem material from the leaf material to provide a tea plant source rich in stem; (iii) treating the stem source with at least one conventional tea processing unit operation selected from withering, maceration, grinding, steaming, fermentation, firing and infusing.
Thus we have recognised that there is a need to provide new materials enriched with tea compounds. We have also recognised that there is a need for a process for obtaining tea compounds from tea stem that does not require the use of large amounts of a solvent. We have found that such needs may be met by employing a process wherein juice is expressed from tea stem.